Pngcrush is an optimizer for PNG (Portable Network Graphics) files.
It can be run from a commandline in an MSDOS window, or from a UNIX or
LINUX commandline. Its main purpose is to reduce the size of the PNG
IDAT datastream by trying various compression levels and PNG filter
methods. It also can be used to remove unwanted ancillary chunks, or
to add certain chunks including gAMA, tRNS, iCCP, and textual chunks.
